Search Results (19)

The litter decomposition of plant leaves is a vital process in carbon (C) and nitrogen (N) cycling in global terrestrial ecosystems. However, previous assessments of the key determinants of the N deposition effects of litter decomposition have been more controversial. In this meta-analysis, we compared the overall effects of N addition on the litter decomposition rates, litter nutrient content (C and N), and litter constituent (lignin and cellulose) residual rates using a log response ratio approach. Our results showed that exogenous N addition increased the N content and inhibited lignin degradation in litter. N deposition decreased the leaf litter decomposition rate by increasing the lignin and N residues and decreasing the litter C content and soil pH. The analysis also concluded that the initial litter C/N ratio, lignin content, and soil pH were main factors in mediating the effect of N deposition on litter decomposition rate. Overall, the results of this study indicate that N deposition can slow decomposition rates by inhibiting N release and lignin degradation of litter. Notably, these results emphasize that the effect of N deposition on litter decomposition mainly depends on the endogenous quality of the litter and soil pH in the decomposition environment. Full article

Co-application of sewage sludge (SS) with biochar in landscape/forestry soil is a common strategy for enhancing soil fertility and reducing the bioavailability of potential toxic elements (PTEs) derived from SS, such as Cd, Pb, Cu, Zn, and Ni. However, due to variability of biochar quality and uncertainties in responses of different plant species, whether the co-application benefits the landscape/forestry plant system remains elusive. Here, we tested the effectiveness of three types of biochar (SS-derived biochar (SB), rice straw-derived biochar (RB), and litter-derived biochar (LB)), which were added to soil amended with SS at 50% (w/w) at rates of 1.5%, 3%, and 4.5% as growth media for the landscape plant Aglaonema modestum (A. modestum). We analyzed the substrate’s physicochemical properties and assessed the alleviation of phytotoxicity by biochar application. A significant increase in the fertility index of substrate was observed in all the treatments with biochar addition. The addition of biochar reduced the potential mobility of PTEs while increasing their residual fraction in media. Nonetheless, it has been found that the addition of biochar has ineffective or even negative effects on A. modestum growth (height, biomass, root length) and nutrient absorption. Importantly, the reduction in root biomass and the increased activity of root antioxidant enzymes (SOD, POD, CAT, and MDA) indicate contamination stress of biochar on the roots of A. modestum. Toxic elements of concern—namely Cu, Cd, and Pb—were not significantly higher in tissues of A. modestum saplings planted in biochar-SS-amended soil. However, elevated levels of other elements that may pose toxicity concerns, such as Ni and Zn, increased in tissues at high biochar dosages. Based on the Entropy–Weight TOPSIS method, it was further confirmed that compared to the treatment without biochar, all treatments except for 3.0% LB application resulted in poorer A. modestum comprehensive growth. Our results emphasize the need for detailed research on the response of specific plants to biochar in specific environments, including plant adaptability and the unexplored toxicity of biochar, to understand the large variations and mechanisms behind these ineffective or negative effects before the large-scale co-utilization of SS and biochar in landscape/forestry soils. Full article

Litter decomposition is important for understanding the effects of habitat on nutrient cycling. In this study, we investigated the decomposition characteristics, decomposition variability, and regulatory factors restricting the decomposition rates of leaf litter in three different habitats: a flood disturbance habitat, an arid habitat, and a high-salinity habitat. The litter decomposition rates of the habitats decreased in the following order: flood disturbance habit > arid habitat > high-salinity habitat. The organic carbon, total nitrogen, and lignin residues of the litter during the decomposition period were highest in the high-salinity habitat. The litter quality was the main regulator of the release of phosphorus and cellulose residues, which exhibited different release processes and patterns in these three habitats. The litter decomposition coefficient was negatively correlated with litter carbon residue in the flood disturbance habitats, the lignocellulose index in the arid habitats, and soil urease in the high-salinity habitats. It was positively correlated with the lignocellulose index in flood disturbance habitats and litter carbon residue in high-salinity habitats. The litter quality in the flood disturbance area played a significant role in litter decomposition, while environmental quality and litter quality were the dominant factors under arid and high-salt conditions. Litter quality in the flood disturbance area played a significant role in litter decomposition, while both environmental quality and litter quality were the dominant factors under arid and salt conditions. Full article

In order to understand the role of microorganisms in litter decomposition and the nutrient cycle in volcanic forest ecosystems, the dominant forest species Larix gmelinii in the volcanic lava plateau of the Wudalianchi volcano was considered as the research object. We analyzed the response of bacterial community structure and diversity to litter decomposition for 1 year, with an in situ decomposition experimental design using litter bags and Illumina MiSeq high-throughput sequencing. The results showed that after 365 days, the litter quality residual rate of Larix gmelinii was 77.57%, and the litter N, P, C:N, C:P, and N:P showed significant differences during the decomposition period (p < 0.05). The phyla Cyanobacteria and the genus unclassified_o_Chloroplast were the most dominant groups in early decomposition (January and April). The phyla Proteobacteria, Actinobacteriota, and Acidobacteriota and the genera Massilia, Pseudomonas, and Sphingomona were higher in July and October. The microbial communities showed extremely significant differences during the decomposition period (p < 0.05), with PCoa, RDA, and litter QRR, C:P, and N as the main factors driving litter bacteria succession. Microbial functional prediction analysis showed that Chloroplasts were the major functional group in January and April. Achemoheterotrophy and aerobic chemoheterotrophy showed a significant decrease as litter decomposition progressed. Full article

Small ruminants, such as sheep (Ovisaries) and goats (Capra hircus), contribute to approximately 475 million metric tons of carbon dioxide equivalent (MtCO₂e) greenhouse gas (GHG) emissions, accounting for approximately 6.5% of the global emissions in the agriculture sector. Crop residues, silage, grasses, hay, browse, plant leaves, shrubs, agro-industrial by-products, poultry litter, and other alternative feed sources are frequently utilized for small ruminant production. The use of these valuable alternative feeds can significantly improve animal productivity and reduce carbon footprints and GHG fluxes, making it both environmentally friendly and cost-effective. Additionally, these alternative feeds possess antioxidant, antimicrobial, and antiseptic properties that can enhance the quality of the meat and milk produced. By impacting the bacteria involved in ruminal biohydrogenation, alternative feeds can reduce methane emissions and contribute to a decrease in the carbon footprint. Overall, the use of alternative feed sources for small ruminants generally improves their apparent nutrient digestibility and productivity, and has an impact on the production of greenhouse gases, especially methane. Finally, this review recommends evaluating the economic analysis of reducing methane emissions in small ruminants by utilizing different feed sources and feeding techniques. Full article

The reserve of litter is expected to be reduced on the forest floors of pine plantations dually for the prevention of high risks of forest fires and with a more practical probability of reuse. Lignin and cellulose are the two key constitutive components in litter residues that account for the highest proportion of carbon but are the last to be fully decomposed. The existing trials started examining the mechanisms behind decomposing these two components in response to the combined driving forces of microclimatic factors, forest structure, and stand properties. However, the results were mostly limited to a local-scale ecosystem, and the evidence was reported to be highly scattered across varied conditions globally. Awareness about the combined effects of the driving forces behind the lignin and cellulose contents in the litter of plantations on a large scale is still scarce. In this study, a total of 60 Pinus tabuliformis Carr. plantations (40-year-old) were investigated for their litter quality, regional meteorological factors, soil properties, and stand structure in a provincial area across Liaoning, northeast China. High lignin (40%–43%) and cellulose contents (15%–20%) were found to be located mainly in stands around the biggest city of Shenyang. Rainfall was a key factor that determined the decomposition, but neither the forest structure nor soil nutrient content generated direct effects on the two litter components. The combined factors of low soil pH (~5.8) and high rainfall (~3.0 mm per day) together mainly accounted for the promotion of natural litter decomposition. Full article

The Quick Wash (QW) treatment extracts phosphorus (P) from manure and municipal sludge (MS), producing an organic acidified by-product with adequate nitrogen (N):P ratio to meet crop N requirements. Yet, data on crop response to N using QW by-products are lacking. We evaluated the response of annual ryegrass (Lolium multiflorum Lam.) and potential N leaching in sandy soil to N applications using raw wastes, their corresponding QW by-products, and ammonium sulfate (AMS) fertilizer. Treatments included a control (no amendment added), raw and acid-washed chicken litter, dairy and swine manure, MS, and AMS at 100, 200, and 400 kg N ha⁻¹. We found no significant differences in annual ryegrass yield and N uptake between the raw and acidified organic QW by-products. However, ryegrass produced 4–30% more biomass with AMS than organic amendments. The total residual soil inorganic N under AMS treatments ranged between 6.3 and 67.9 mg pot⁻¹ and accounted for 5–17% of the total N applied, but it was <1% for all the organic amendments. We found no differences in soil N leaching between raw and acid-washed forms of each organic soil amendment. Our results indicated that acidified organic QW by-products can improve environmental quality by substantially reducing the amount of applied P with no penalties for crop yield losses compared to raw manure and MS. Full article

Primary forest conversion greatly influences soil organic carbon (SOC) sequestration. However, our understanding of how primary forest conversion affects SOC fractions and chemical component evenness remains limited. We examined how primary forest conversion (from primary mixed broadleaved Korean pine forest to secondary broadleaved forest and coniferous plantation) affects free particulate OC (POC), aggregate-occluded POC, mineral-associated OC (MAOC), and their chemical component evenness via plant inputs (e.g., litter and fine roots) and microbial properties (e.g., microbial biomass and residue C) in Northeast China. Primary forest conversion led to a large increase in litter and fine root quality (lower C/N ratio), SOC, and MBC of secondary forests and a reduction in litter and fine root quantity and quality, SOC, MBC, and microbial residue C of plantations, which drove changes in POC and MAOC. As a result, after conversion to secondary forests, free POC decreased by 20.3% and aggregate-occluded POC increased by 57.2%. After conversion to plantations, free POC increased by 49.1%, while aggregate-occluded POC and MAOC decreased by 42.4% and 9.0%, respectively. Free POC was negatively correlated with fine root biomass. Aggregate-occluded POC and MAOC were positively correlated with litter and fine root quality, MBC, and microbial residue C. Meanwhile, forest conversion decreased the evenness of free and aggregate-occluded POC chemical components in secondary forests, with O-alky C being higher and aromatic C being lower, while MAOC was not affected by forest conversion. The evenness of free and aggregate-occluded POC chemical components was associated with litter and fine root quality, and that of MAOC was associated with MBC and microbial residue C. High-quality plant inputs benefit OC sequestration in soil aggregates and MAOM through microbial assimilation and residue accumulation after primary forest conversion. Future forest management should consider tree species with high-quality input as a possible compensation for climate change by sequestering more OC in soil aggregates. Full article

Earthworms and soil microorganisms contribute to soil health, quality, and fertility, but their importance in agricultural soils is often underestimated. This study aims at examining whether and to what extent the presence of earthworms (Eisenia sp.) affected the (a) soil bacterial community composition, (b) litter decomposition, and (c) plant growth (Brassica oleracea L., broccoli; Vicia faba L., faba bean). We performed a mesocosm experiment in which plants were grown outdoors for four months with or without earthworms. Soil bacterial community structure was evaluated by a 16S rRNA-based metabarcoding approach. Litter decomposition rates were determined by using the tea bag index (TBI) and litter bags (olive residues). Earthworm numbers almost doubled throughout the experimental period. Independently of the plant species, earthworm presence had a significant impact on the structure of soil bacterial community, in terms of enhanced α- and β-diversity (especially that of Proteobacteria, Bacteroidota, Myxococcota, and Verrucomicrobia) and increased 16S rRNA gene abundance (+89% in broccoli and +223% in faba bean). Microbial decomposition (TBI) was enhanced in the treatments with earthworms, and showed a significantly higher decomposition rate constant (k_TBI) and a lower stabilization factor (S_TBI), whereas decomposition in the litter bags (d_litter) increased by about 6% in broccoli and 5% in faba bean. Earthworms significantly enhanced root growth (in terms of total length and fresh weight) of both plant species. Our results show the strong influence of earthworms and crop identity in shaping soil chemico-physical properties, soil bacterial community, litter decomposition and plant growth. These findings could be used for developing nature-based solutions that ensure the long-term biological sustainability of soil agro- and natural ecosystems. Full article

The initial carbon (C) quality of plant litter is one of the major factors controlling the litter decomposition rate and regulating C sequestration, but a comprehensive understanding is still lacking. Here, we used proximate analysis and ¹³C nuclear magnetic resonance (NMR) with spectral editing techniques to quantify the variations in the initial C quality for four dominant species (fir: Abies faxoniana Rehd. et Wils.; spruce: Picea asperata Mast; willow: Salix paraplesia Schneid; and rosa: Rosa omeiensis Rolfe.), including the organic compositions and C-based chemical structures of newly shed foliar litter over eight months in an alpine forest on the eastern Tibetan Plateau. The results indicated that the fractions of acid-soluble extractives (ASE) and acid-unhydrolyzable residues (AUR) were the main fractions of organic components, and aliphatic C and O-alkyl C were the main functional C groups for all plant species. Under the effects of the plant species, higher levels of ASE (37.62%) and aliphatic C (35.44%) were detected in newly shed rosa foliar litter, while higher levels of AUR (fir: 37.05%; spruce: 41.45%; and willow: 40.04%) and O-alkyl C (fir: 32.03%; spruce: 35.02%; and willow: 32.34%) were detected in newly shed fir, spruce and willow foliar litter. Moreover, the A/O-A and HB/HI ratios in rosa litter were 0.88 and 1.15, respectively, which were higher than those in fir, spruce and willow litter. The C quality of newly shed foliar litter varied seasonally due to the litter quality and environmental conditions, especially nitrogen (N), dissolved organic carbon (DOC), manganese (Mn) and monthly air temperature. We also found that C loss during 4-year litter decomposition was highly related to the aromatic C and phenolic C contents in newly shed foliar litter, suggesting that litter decomposition was strongly controlled by the initial recalcitrant C fractions. We conclude that the C quality of newly shed foliar litter in rosa might be structurally stable and more resistant to degradation than that of fir, spruce and willow, which contain abundant labile C fractions, and the initial recalcitrant C fractions are closely related to C loss during litter decomposition, which might contribute to soil C sequestration in alpine forests. Full article

Soil microorganisms and dissolved organic matter (DOM) play vital roles in nutrient cycling and maintaining plant diversity. The aim of this study was to clarify the relationship between DOM component characteristics and microbial community structure in the soil of Larix principis-rupprechtii Mayr. plantations. We quantified the responses of the soil microbial and DOM characteristics to stand age in a plantation forest ecosystem using phospholipid fatty acid (PLFA) analyses, ultraviolet-visible spectroscopy, and fluorescence spectroscopy. Three humic-like components and a fulvic-like component were identified from the soil samples, and humic-like substances were the dominant component of the soil DOM of the stands of different ages. The fluorescence index showed that the sources of soil DOM in the stands of different ages throughout the growth stages may be mostly plant residues, with very little contribution from microbial sources. Furthermore, the results demonstrated that stand age and growth season had a significant effect on the contents of the soil PLFA biomarkers of L. principis-rupprechtii Mayr. Additionally, significantly higher contents of different species of soil PLFA biomarkers were observed in the young forest (17a) than in the sapling forest (7a) and half-mature forest (27a), suggesting that stand age differences in the quality and quantity of larch litter and soil physicochemical characteristics affect the microbial community structure. Redundancy analysis (RDA) showed that changes in the soil DOM quality and components that were driven by growth season and stand age were the major drivers of variations in the soil microbial community structure in the study region. Overall, the seasonal variations in DOM quality and components may contribute to the variability of soil microorganisms, and the soil microbial responses to tree age will depend upon the provisioning of these resources. Full article

Climate and litter chemistry are major factors influencing litter decay, a process mediated by microbes, such as fungi, nitrogen-fixing bacteria and ammonia-oxidizing bacteria. Increasing atmospheric CO₂ concentrations can decrease nitrogen (N) and increase condensed tannin (CT) content in foliar litter, reducing litter quality and slowing decomposition. We hypothesized that reduced litter quality inhibits microbes and is the mechanism causing decomposition to slow. Litterbags of Douglas-fir needles and poplar leaves with a range of N (0.61–1.57%) and CT (2.1–29.1%) treatment and natural acid unhydrolyzable residue (35.3–41.5%) concentrations were placed along climatic gradients in mature Douglas-fir stands of coastal British Columbia rainshadow forests. The structure (diversity, richness and evenness) and composition of microbial communities were analyzed using DGGE profiles of 18S, NifH-universal and AmoA PCR amplicons in foliar litter after 7, 12, 24 and 43 months of decay. High CT and low N concentrations in leaf litter were associated with changes in microbial community composition, especially fungi. Contrary to our hypothesis, high CT and low N treatments did not inhibit microbial colonization or diversity. The joint effects of air temperature and soil moisture on microbial community composition at our sites were more important than the effects of initial litter chemistry. Full article

Returning crop residues to agricultural fields can accelerate nutrient turnover and increase N₂O and NO emissions. Increased microbial respiration may lead to formation of local hotspots with anoxic or microoxic conditions promoting denitrification. To investigate the effect of litter quality on CO₂, NO, N₂O, and N₂ emissions, we conducted a laboratory incubation study in a controlled atmosphere (He/O₂, or pure He) with different maize litter types (Zea mays L., young leaves and roots, straw). We applied the N₂O isotopocule mapping approach to distinguish between N₂O emitting processes and partitioned the CO₂ efflux into litter- and soil organic matter (SOM)-derived CO₂ based on the natural ¹³C isotope abundances. Maize litter increased total and SOM derived CO₂ emissions leading to a positive priming effect. Although C turnover was high, NO and N₂O fluxes were low under oxic conditions as high O₂ diffusivity limited denitrification. In the first week, nitrification contributed to NO emissions, which increased with increasing net N mineralization. Isotopocule mapping indicated that bacterial processes dominated N₂O formation in litter-amended soil in the beginning of the incubation experiment with a subsequent shift towards fungal denitrification. With onset of anoxic incubation conditions after 47 days, N fluxes strongly increased, and heterotrophic bacterial denitrification became the main source of N₂O. The N₂O/(N₂O+N₂) ratio decreased with increasing litter C:N ratio and C_org:NO₃⁻ ratio in soil, confirming that the ratio of available C:N is a major control of denitrification product stoichiometry. Full article

Understanding phosphorus (P) dynamics in tropical sandy soil treated with organic residues of contrasting quality is crucial for P management using organic amendments. This research determined P fractions in a tropical sandy soil under the application of organic residues of different quality, including groundnut stover (GN), tamarind leaf litter (TM), dipterocarp leaf litter (DP), and rice straw (RS). The organic residues were applied at the rate of 10 t DM ha⁻¹ year⁻¹. The P fractions were examined by a sequential extraction procedure. Organic residue application, regardless of residue quality, resulted in P accumulation in soils. For unamended soil, 55% of total P was mainly associated with Al (hydr)oxides. Organic residue application, regardless of residue quality, diminished the NH₄F-extractable P (Al-P) fraction, but it had a nonsignificant effect on NaOH-extractable P (Fe-P). The majority of Al-P and Fe-P fractions were associated with crystalline Al and Fe (hydr)oxides. NH₄Cl-extractable P (labile P), NaHCO₃-extractable P (exchangeable P and mineralizable organic P), HCl-extractable P (Ca-P), and residual P fractions in soil were significantly increased as a result of the incorporation of organic residues. The application of organic residues, particularly those high in ash alkalinity, increase soil pH, labile P, and Ca-P fractions. In contrast, applications of residues high in lignin and polyphenols increase residual P fraction, which is associated with organo-mineral complexes and clay mineral kaolinite. Full article

Plant litter, such as fallen leaves, branch trimmings, and other yard waste, plays important roles in both natural and man-made ecosystems. However, due to common aesthetic perceptions, land-owners or managers of many residential gardening and municipal landscaping systems consider these organic residues a burden, and therefore, clear them from the ground and dispose of them off-site. The removal of these organic resources increases the system’s environmental footprint, decreases its sustainability, and negates the provision of important ecosystem services. At the same time, retaining these organic materials on-site could provide the system with substantial benefits. The most obvious effect is the ground surface shading, which decreases direct solar radiation to the soil, lowers soil temperature, lessens evaporation rates, decreases risk of soil salinization, and improves water-use efficiency. Ground surface mulching likewise prevents the raindrop splash impact, negates the formation of sealed mechanical crusts, improves water infiltrability, and reduces water runoff and soil erosion. Another benefit is the on-site decomposition of organic materials, which improves soil quality by elevating organic carbon concentration and contributing to nutrient cycling. Vegetation patches in such systems encompass "engineered fertility islands", which can be defined as highly productive, healthy, and functioning habitats. Further, over time, these systems require less maintenance. This management practice is crucial for tree- or shrub-dominated gardening and landscaping systems in drylands, where water availability is the major limiting factor of vegetation growth. However, global climate change, in which extended parts of the world experience increasing temperatures and decreasing precipitation rates, makes this practice relevant for other climatic regions as well. Full article